The relationship between diagnostic information obtained from three tests for detecting mild diabetes mellitus.

The purpose of the study was to evaluate and compare the most commonly used criteria for the interpretation of the oral (OGTT) and intravenous (IVGTT) glucose tolerance tests and the intravenous tolbutamide test (IVTT) and to establish the criteria that give the highest degree of diagnostic agreement. The highest degree of diagnostic agreement was obtained with the following limits: a) blood glucose greater than or smaller than or equal to 120 mg/100 ml within 2 1/2 h after a 100 g OGTT together with b) a k-value of greater than or smaller than or equal to 1.05 as a limit for a 25 g IVGTT and c) a 30 min blood glucose level as percentage of fasting of greater than or smaller than or equal to 77 as limit for a 1 g IVTT. Using these criteria the three tests deemed the same subjects either diabetic or nondiabetic in about 2/3 of the cases. The best correlation between the blood glucose values of the OGTT and the k-values of the IVGTT and the 30 min values of the IVTT was obtained using the blood glucose concentrations of the last part of the OGTT. The 2 and the 3 hr values were however equal to the 2 1/2 hr values with regard to the degree of correlation with the values of the intravenous test. The results indicated that the diagnostic disagreement reported previously between the three tests may partly be due to the use of blood glucose values in the first part of the OGTT for the classification of the test and partly due to the screening limits chosen for interpretation of the three test.